Rigorous study has been carried out on this sundial boss, and will appear in Bishop & Davis Bulletin of the British Sudial Society (forthcoming) 2011.
Analysis of the dial projections has suggested a latitude of 55° 48', just south of Edinburgh, fitting with this style of obelisk multiple dial common in Scotland circa 1630-1730. The presence of London, Acra, Ierus[alme], [R?]ome, Paris, Tangier, Madera [sic] on the dials is of interest: Acra was one of the sites on the Guinea coast specified in the Charter of the Royal African Company in 1672.
The boss was discovered by the present owner, half-buried in the ground at Walton Lodge, Great Amwell in 1974, was recently identified as part of a Scottish renaissance sundial, the rest of the obelisk is unlocated. It is the find location that provides us with the final clue as to its possible manufacture: Walton Lodge was the one time residence of the Mylne family. Robert Mylne (1633-1710) was the last Master Mason to the Crown of Scotland. His uncle John Mylne (1611-1667) being responsible for the earliest dated dial of this type at Drummond Castle (1630).